Apparatus for automatically determining and setting length of charging time



Dec. 9, 1969 R. s. MaccREA APPARATUS FOR AUTOMATICALLY DETERMINING AND SETTING LENGTH OF CHARGING TIME Filed NOV. 22, 1967 E INVENTOR Efe/Meo 6. MAcC'EAE A04/ua( 41.7,

A 7' TGPMEIJ United States Patent O 3,483,460 APPARATUS FOR AUTOMATICALLY DETERMIN- ING AND SETTING LENGTH OF CHARGING TIME Richard S. MacCrea, New Brighton, Minn., assigner to Marquette Corporation, Minneapolis, Minn., a corporation of Delaware Filed Nov. 22, 1967, Ser. No. 685,173 Int. Cl. H02j 7/04, 7/16 U.S. Cl. S20-31 10 Claims ABSTRACT OF THE DISCLOSURE Battery charging apparatus in which a time controls the length of charging. The apparatus initially uses a motor to adjust the time from an off position to an initial timing position. The adjustment depends upon the output voltage of the battery under load.

BACKGROUND OF THE INVENTION In charging a battery, it is very desirable that the charging time bear a predetermined relation to the condition of the battery to be charged. One way in which to measure this condition is to place the battery under load and then measure the voltage across it. It has been proposed to employ a voltmeter for this purpose and to employ a timer having a variable impedance which is adjusted in accordance with the adjustment of the time. The variable impedance is connected to the battery voltage and to the voltmeter in such a way that the elTect of the battery voltage on the voltmeter is modied in accordance with the setting of the variable impedance. By adjusting the timer until the voltmeter reads a predetermined value, the timer tends to be set for a timing period corresponding to the battery voltage under load. When the voltmeter reading reaches this predetermined value, a manually operable switching device is then actuated to disconnect the load from the battery and to initiate the charging operation which lasts for the time period determined by the setting of the timer. Such an arrangement is shown in the Pugh Patents 2,431,707 and 2,432,069.

It has further been proposed in a co-pending application of Joseph H. Schaefer, led of even date herewith, to provide an arrangement in which when the timer has been manually set to the desired position, a relay is automatically operated to disconnect the load and start the timing operation. This has the advantage of making the system more automatic and lessening the chance for human error.

SUMMARY OF THE INVENTION In the present arrangement, the timer is automatically adjusted by a motor which continuously adjusts the timer until such time as the timer is set for a timing period corresponding to the voltage across the battery to be charged. As soon as this condition is reached, the motor is automatically deenergized and the timing operation is automatically started. In this way, it is assured that the timer will be set for a timing period corresponding to `the condition of the battery and there is no danger of the timer being set for an excessively long period due to the operator adjusting the timer beyond the desired timing period. Furthermore, I employ an element having a standard voltage drop thereacross so that it is assured that the response of the apparatus to the voltage of the battery to be charged will aways be constant without any variations due to loss of calibration. l

The apparatus is designed so that it is only necessary to push a momentary starting device. After that, the entire operation is automatic except for setting the charging rate.

3,483 ,460 Patented Dec. 9, 1969 ICC Simply, this is accomplished by providing a switching device such as a relay which is actuated upon operation of the momentary starting device and remains in this actuated position until the timer is set. The subsequent release of the relay initiates the charging operation.

A further feature of my invention is that I employ a fan for cooling the apparatus which is energized through one circuit during the time that the timer is being set and through another circuit during the charging operation.

More specically, my arrangement employs a one-way clutch between the motor and the timer so that after the motor has set the timer, it is free to continue to its oif position without being affected by the motor.

A further feature of my invention is that I employ a variable load resistance and a variable Calibrating resistance and a selector switch so that if the apparatus is to be used with 12-volt batteries, for example, one value of load resistance and one value of Calibrating resistance are connected in to the apparatus; whereas, if the battery to be charged is a 6-volt battery, another value of load resistance and another value of Calibrating resistance are connected into the apparatus.

Various other features of my invention will be apparent from a consideration of the accompanying specication, claims and drawing.

BRIEF DESCRIPTION OF THE DRAWING The single figure of te drawing shows my improved battery charger is schematic form, the charging apparatus being shown as connected to a battery to be charged.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, the charging apparatus is shown as being located within a housing 10 located in dotted lines. The charging apparatus has output terminals 11 and 12 which are shown as connected to a battery 13 to be charged. The apparatus also has input terminals 14 and 15 which are adapted to be connected to a suitable source of commercial power, such as power leads 16 and 17.

Referring to the charging apparatus proper, the charging current is derived from a step-down transformer 19 having a primary winding 20 and a low voltage secondary winding 21` The left-hand terminal of the primary winding 20 is connected by conductors 22, 23, 24, 25 and 26 to the input terminal 14 which, in turn, is connected to power supply line 16. The primary winding has four taps 27, 28, 29 and 30, one or the other of which is selectively engaged by a switch blade 31 which, in turn, is connected through various switches, to be presently described, to the other input terminal 15 which, in turn, is connected to the other line wire 17. The selector switch 31 is placed in various position depending upon the charging rate desired, it being obvious that the secondary voltage produced by secondary winding 21 is determined by the position of switch 31.

The secondary winding 21 is center tapped at 36 and is connected through a conductor 37, a switch 38 within a polarity protector unit 39, and conductor 40 to a negative bus conductor 41 leading to the output terminal 11. The opposite terminals of secondary winding 21 are connected through rectifying diodes 42 and 43 to a positive bus 13. Since such polarity protectors are old, the details of unit 39 are not disclosed and will not be discussed here- It will be readily apparent from the above description that when the primary winding 20 of the transformer 19 is energized and the output terminals 11 and 12 are connected in the proper polarity manner to the battery 13 so as to cause closure of switch 38, a D.C. voltage will be applied to the terminals of the battery 13 to charge the same. As mentioned above, the lower bus conductor 44 will be positive and the upper bus conductor 41 will be negative.

As pointed out previously, the apparatus of the present invention employs a timer for determining the length of time during which the charging operation takes place. This timer is of the type which can be set for any desired timing period. The timer is generally designated by the reference numeral 46 and has an output shaft schematically shown at 47, this output shaft carrying a cam 48 which is designed to cooperate with a switch blade 49 cooperating with a xed contact 50. The timer is shown in its off position at which time the cam 48 is in the position in which switch blade 49 is held out of contact with contact 50. The shaft 47 is also connected to a pointer 52 cooperating with a circular scale 53 to indicate the desired timing period. As indicated by the legends on the drawing, the particular timer emp-loyed may, for example, have a timing range of from zero to two hours. Timer 46 is preferably of the type employing an electric motor 45 which tends to turn the shaft 47 from the initial timing position to its off position. The shaft 47 is connected to the motor 45 through a slip clutch which enables the shaft 47 carrying cam 48 and pointer 52 to be adjusted for any desired timing period. The shaft 47 is, in turn, connected to a setting shaft 55 in a one-way clutch 56 to a motor 57 which is designed, when it is energized, to drive shaft 47. The function of the one-way clutch 56 is to permit the shaft 47 to be driven by timer 46 ahead to the off position without being affected by motor 57. In other words, the one-way clutch 56 is effective to transmit the motion of the motor 57 to the shaft 47 in a direction to advance the selector timer but does not offer any resistance to continued motion of the shaft 47 in the same direction independent of the motor. Also connected to the setting shaft 55 through a suitable mechanical connection 60 is the slider 61 of a rheostat 62 having a circular resistor 63 with which the slider 61 cooperates. Resistor 63, while generally circular, does not extend continuously for 360 but has a slight interruption just before the off position of the slider 61, in which position the slider 61 is shown in the drawing. As the timer is set by rotation of shaft 47, the slider 61 is moved in a counterclockwise direction on resistor 63 for a purpose to be presently described.

A relay 66 is employed to control the operation of the timer and motor 57 and to control the energization of the primary winding 20 of the transformer 19. This relay comprises a relay winding 67 and a pair of relay switch blades 68 and 69. The relay swtch blades 68 and 69 are biased into engagement with fixed contacts 70 and 71, respectively, and are adapted upon energization of winding 67 to be moved into engagement with fixed contacts 72 and 73.

A manually operable starting switch 75 is employed to initially start the apparatus. This comprises a pair of switch blades 76 and 77 which are actuable by a manual actuator 78. Switch blades 76 and 77 are designed to be engaged with xed contacts 79 and 80, respectively, when the manual actuator 78 is depressed. The switch 75 is provided `with a suitable biasing means, not shown, which is effective to disengage switch blades 76 and 77 from fixed contacts 79 and 80 as soon as the manual actuator 78 is released.

The energization of relay winding is directly controlled by a P-N-P transistor 84 which, as will be presently de- 4 scribed, is connected directly in series with relay winding 67.

Power for the control circuit means including transistor 84 is supplied by a step-down transformer 85 having a primary winding 86 and a low voltage secondary winding 87. The upper terminal of primary winding 86 is connected through a conductor 89 to the input terminal 14. The lower terminal of primary winding 86 is adapted to be connected through a switching arrangement described later to the other input terminal 15.

The opposite terminals of low voltage secondary winding 87 are connected through rectifying diodes 91 and 92 to the bus conductor 44. The center tap of secondary winding 87 is connected to a conductor 93. A filter condenser 94 is connected between conductor 93 and the bus conductor 44 to iilter out ripples in the rectified voltage output applied between conductors 93 and 44. It will be noted that the diodes 91 and 92 are so poled that the effect of secondary 87 and diodes 91 and 92 is to maintain the conductor 93 positive with respect to the positive bus conductor 44.

Referring to the connections between vthe transistor 84 and the relay winding system 67, the emitter is connected to conductor 93, while the collector is connected to the lower terminal to winding 67. The upper terminal of -winding 67 is connected to the bus conductor 44. It will be seen that since conductor 93 is positive with respect to conductor 44, a circuit exists from the upper conductor 93 `through the emitter and collector circuit of transistor 84 and the relay winding 67 to the bus conductor 44. When the primary winding 86 is energized so as to apply power to the transistor 84 and the transistors biased so as to be conductive, an energizing circuit is established for the relay coil 67 through the emitter-collector circuit of transistor 84. Diode 95 is connected between the collector of transistor 84 and the bus conductor 44 so as to be eiectively in parallel with the relay coil 67. The effect of diode 95 is to prevent the inductive effects of the relay operation from damaging the transistor 84.

The conductivity of transistor 84 is controlled by an N-P-N transistor 97, the collector of which is connected through a resistor 98 and a second resistor 99 to the positive bus conductor 93. The emitter of transistor 97 is connected through a biasing diode to the bus conductor 44. The base. of transistor 84 is connected to the junction of resistors 98 and 99. When current flows through the collector-emitter circuit of transistor 97, a voltage drop is produced across transistor 99 which in turn causes the P-N-P transistor 84 to be conductive. Thus, transistor 84 is conductive whenever transistor 97 is conductive.

The conductivity of transistor 97 is in turn controlled by a further transistor 102, which is also an N-P-N transistor. The emitter of this transistor is connected to the bus conductor 44 while the collector is connected through resistor 103 to the positive conductor 93. The collector of transistor 102 is further connected to the base of transistor 97. When transistor 102 is conductive, a suicient voltage drop exists across resistor 103 to prevent current flow through the base emitter circuit of transistor 97 and, hence, to maintain it nonconductive. Thus, transistor 102 must be nonconductive in order for transistor 97 and, in turn, transistor 84 to =be conductive.

The conductivity of transistor 102 and hence of transistors 97 and 84 is controlled by a network including rheostat 62 and a Zener diode 106. Zener diode 106 is connected in series with resistor 107 between the positive bus conductor 93 and the bus conductor 44. There is thus a constant voltage drop across Zener diode 106 to maintain a constant potential at junction point 108 between the Zener diode 106 and resistor 107. Junction point 108 is thus maintained `at a constant, positive potential with respect to bus conductor 44.

Very broadly, the resistor 63 of rheostat 62 is connected in series with Zener diode 106 between the negative. output terminal 11 and the positive output terminal 12 through a resistance network generally indicated by the reference numeral 109. This resistance network comprises a resistor 110, a rheostat 111, a second rheostat 112 and a resistor 113. As will be presently explained, provision is made for effectively short circuiting rheostat 111 and resistor 110 under certain conditions of operation.

Connected in parallel with resistor 63 is a rheostat 115. The right-hand terminals of resistor 63 and rheostat 115 are connected together and through a resistor 116 to the bus conductor 41 leading to the negative output terminal 11.

The lower terminal of resistor 113 is connected to junction point 108 and through the. Zener diode 106 to bus conductor 44 leading to the positive terminal 12. The junction of resistor 110 with the connection between slider `61 Of rheostat 62 and rheostat 115 is indicated by the reference numeral 117. Junction point 117, as will be presently described, constitutes la junction point of a voltage divider in one leg of which the rheostats 62 and 115 are connected, along with resistor 116. In the other leg of the voltage divider, rheostat 112, resistor 113 and Zener diode 106 are connected. Under certain conditions, this rleg of the voltage divider also includes the resistor 110 and rheostat 111. The junction point 117 of this voltage divider is connected through conductors 119 and 120 to the base of transistor 102.

It has been pointed out that under certain conditions resistor 110 and rheostat 111 are sliort-circuited. This is accomplised by a switch 125 having a pair of switch blades 126 and 127. Switch blade 126 is adapted to move between the position shown in which it is in engagement with a contact 128 and a second position in which it is in engagement with a dead contact 129. Similarly, switch blade 127 is movable between a position in which it is in engagement with a contact 130 and a second position in which it is in engagement with a contact 131. The two switch blades, 12.6 and 127, are connected together by an operating shaft 132 which in turn is connected to a manual actuator 133 which may take the form of a knob. The switch 125 is operated in accordance with whether the battery being tested is a 6-volt battery or Ia l2-volt battery, the switch -being shown in the position in which the battery being tested is a 12-volt battery. 1n this position, switch blade 126 is in engagement with contact 128 lwhich in turn is connected to the junction of rheostats 111 and 112. With the switch blade in this position, it will be readily apparent that, since switch blade 126 is connected through conductor 119 to the right-hand terminal of resistor 110, rheostats 111 and 112 are short-circuited and are. not included in the voltage divider network. When, however, switch blade 126 is moved to the other position in which it is in engagement with a dead contact 129, the leg of the voltage divider between junction point 117 and bus conductor 44 includes both resistor 110 and rheostat 111. The purpose of short-circuiting resistor 110 and rheostat 111 when the system is being operated with a l2-volt battery is to change the sensitivity of the. voltage divider network to compensate for the difference in voltage of the battery being tested.

The switch -blade 127 controls the energization relay 140 which is one of a pair of relays 140 and 141. Relay 140 has a relay winding 142 and a normally open switch 143 which is closed upon energization of relay coil 142. Similarly, relay 141 comprises a relay coil 144 and a switch 145 which is closed upon energization of coil 144. Relay coil 144 receives current directly from bus conduc tor 44 and from bus conductor 93 by way of conductors 160, 173 and 172 whenever power transformer 85 is energized. As will be presently described, only relay 141 is energized when the switch is in the position shown, that is for 12-volt operation. Both relays 140 and 141 are energized when the switch blade 127 is in the opposite position, that is, for 6-Volt operation. The relays 140 and 141 control each of two lload resistors 147 and 147, one or both of which are connected across the battery during the time period in which the timer is being set for the timing period.

A meter 184 is connected across the output terminals 11 and 12 to determine the voltage across the battery during the charging operation and hence the desired charging operation. The meter is connected between terminals 11 and 12 in series with a resistor 182, a rheostat 183 and a resistor 185.

Switch contact of Switch 125 is connected through a conductor and through a rheostat 181 to the upper terminal of meter 184. The rheostats 183 and 181 act as meter calibration devices for the voltage ranges of batteries to be charged. When the battery charger is used for 6-volt operation, rheostat 181 is not in the circuit, and the meter reads the voltage of the battery while it is under charge so that the operator may determine the proper charging rate. When the charger is used for l2-volt operation, switch blade 127 is in engagement with contact 130', and rheostat 181 is connected in parallel with meter 184 through a circuit extending from the upper terminal of meter 184, through conductor 180, contact 130, switch blade 127, conductor 187, bus conductor 44 and resistor 185 to the lower terminal of meter 184. Under this condition, rheostat 181 acts as a shunt for the meter to allow it to read the higher voltage. The 12-volt range of the -meter is also used to select the proper charging rate for a l2-volt battery by reading the meter while the battery is being charged.

As is common with commercial charging apparatus, a fan 149 is employed. This fan is located within the casing 10 at a point such as to cause a circulation of air at ambient temperature across the elements which tend to heat up such as the rectiiers 42, 43, transformer 19 and the load resistors 147 and 148.

OPERATION When the battery charger is to be used, the rst step is to supply the primary source of power to the unit. This is usually done by simply plugging the unit into a source of commercial line current represented by line wires 16 and 1'7. The battery charger is then connected to a battery 13 which is in need of charging. The polarity protector device 39 insures that the battery will be connected in the proper fashion to the unit before charging is commenced. The operator at this time will also take such other normal steps as are customary in charging a battery. With the initial steps of selecting proper battery voltage range, supplying power to the unit, and connecting the battery to the terminals on the charger, operation is ready to begin.

As has been explained, the advantages of this battery charger include that the starting switch 75 need only be actuated for a moment and then the charging operation is started automatically. This switch 75 will appear on the control panel in one of the standard forms for such a switch, such as a button or a toggle switch. The operator initiates the charging cycle by actuating this switch, closing switch blades 76 and 77.

Closing switch blade 77 to connect with contact 80 supplies the commercial line current to the primary of the control circuit power through transformer 85. It also provides a flow of current to motor 57 and to relay contacts 72 and 73. When the primary of control circuit transformer 85 is energized, the solid state diodes 91 and 92 immediately begin supplying direct current to the control circuit. It is the power supply to the control circuit which is used to hold relay 66 in the energized position while the timer is set for the proper charging time for the battery. This relay is initially energized by the completing of a relay energizing circuit, hereinafter traced, with the closing of switch blade 76 on contact 79. It should also be noted that once the control circuit power supply is encrgized, then relay 141, and also relay 140, if selected by the voltage range switch, will draw in, thus putting load 'i' 148, and if selected, load 147 across the battery which is going to be tested and charged. Thus the initial actuation of switch 75 supplies current to the primary of the control circuit, energizing the relay 66 and connecting one or both of the load resistors 147 and 148 across the battery.

The closing of switch blade 77 to engage with contact 80 establishes a circuit to the primary of the control circuit power transformer as follows: from input terminal through conductors 150l and 151, contact 80, switch blade 77, conductors 152 and 153, primary winding 86 and conductors 89 and 26 to the other input terminal 14.

The closing of switch blade 77 with contact 80 also establishes a circuit to the timer setting motor 57 as follows: from input terminal 15 through conductors 150 and 151, contact 80, switch blade 77, conductors 152, 155 and 156, motor 57 and conductors 157, 24, 25 and 26 to the other input terminal 14.

The closure of Switch blade 76 with contact 79 establishes a circuit to relay winding 67 from the positive conductor 93 of the control circuit through conductors 160 and 161, switch blade 76, contact 79, conductor 162 and relay coil 67 to the opposite bus conductor 44. Since the primary winding 86 has been energized, by closure of switch blade 77 with contact 80, current is available for energization of the relay coil 67 through the circuit just traced. The energization of the relay coil 67 results in switch blades 68 and 69 moving from the position shown in which they are in engagement with contacts 70 and 71 into the position in which they are in engagement with contacts 72 and 73, respectively. The movement of switch blade 68 into engagement with contact 72, establishes a maintaining circuit for the primary winding 86 and the timer setting motor 57. It will be noted that the switch blade 68 is connected to contact 80 of the momentary switch 75 whereas relay contact 72 is connected to the switch blade 77, thus switch blade 68 and contact 72 are in parallel with switch blade 77 and contact 80 so that subsequent separation of switch blade 77 from contact 80 upon release of button 78 will not result in de-energization of either primary winding 86 or the timer setting motor 57. As will be explained in more detail7 the transistor 84 is conductive under these conditions as soon as power is applied between conductors 93 and 44 by reason of the energization of primary winding 86. As previously pointed out, relay coil 67 of relay 66 is in series with the emitter collector terminals of transistor 84 so that the transistor 84 operates to maintain relay coil 67 energized even though switch blade 76 of the momentary Contact switch 75 separates from contact 79. Accordingly, it will be apparent that the switch 75 will need to be closed only momentarily, suicient to energize the primary winding 86 through the switch blade 76 and contact 79 and to allow the relay 67 to be activated. Thereafter, the transistor 84 maintains the relay 66 in its energized position during the initial period in which the timer is being Set.

The movement of relay switch blade 69 into engagement with contact 73 also establishes a circuit to the fan 149 as follows: from input terminal 15 through the conductor 150, switch blade 68, contact 72, conductors 154, 155 and 158, contact 73, switch blade 69, conductor 164, fan 149 and conductors 23, 24, 25 and 26 back to the other input terminal 14. The operation of the fan at this point is desirable, even though the charging operation has not been initiated due to the fact that either one or both of the two load resistors 147 and 148 'are now connected across the battery 13. Assuming that the selector switch 125 is in the 12-volt position shown, in which switch blade 127 is in engagement with contact 130, only relay 144 is energized, relay 144 being connected directly between bus conductors 93 and 44 through the circuit previously traced. The energization of relay winding 144, as a result of energization of primary winding 86, will cause relay switch 145 to close, connecting the 12 volt load resistor 148 `across the battery 13.

If the selector is in the 6-volt position, relay winding 142 is also energized through a circuit extending from bus conductor 93 through conductors 160 and 173, relay winding 142, contact 131, switch blade 127, and conductor 187 to bus conductor 44. Under these conditions, relay switch blade 43 would be closed and the 6-volt load resistor 147 would be connected between the output terminals 11 and 12 in parallel with resistor 148. This reduces the effective load resistance across the output terminals to compensate for the reduced voltage of the battery to be charged.

As a result of th-e various switching operations described, the motor 57 driving the timer setting mechanism is in operation. This motor not only sets the timer 46 but also, through the operative connection 60, rotates the wiper 61 of rheostat 62 in a counter-clockwise direction. The eiect of this will be presently described. Very broadly, the motor 57 continues its operation, setting the timer and movnig the rheostat switch arm 61 until the effect of the latter causes the voltage between the base and emitter of transistor 102 to be such that this transistor becomes conductive. This, in turn, causes transistor 97 and, in turn, transistor 84 to become nonconductive to de-energize the relay 66 at which time the operation of the setting motor 57 is terminated and the charging operation is allowed to proceed. The operation of the voltage divider network .and the effect on the same of rheostat 62 will now be considered in more detail.

As previously explained, the base of translator 102 is connected to junction point 117 between two legs of a voltage divider, in one of which is located the variable resistor 62 and the rheostat 115 in parallel therewith, both being in series with resistor 116. In the other leg, there is located the Zener diode 106, the resistor 113, the rheostat 112 and, in the case of 6-volt operation, the rheostat 111 and resistor 110. This network is connected between the nega-tive bus conductor 4 leading to the negative output terminal 11 and the positive bus conductor 44 leading to the positive output terminal 2. It includes the Zener diode 106, the positive terminal of which is connected to junction point 108 and which is positive with respect to the positive conductor 44. With wiper arm 61 of rheostat 62 in the position shown, which corresponds to the ofi position of the timer, the rheostat 62 offers substantially zero resistance, thus also shunting the rheostat 115. The potential of junction point 117, to which the base of transistor 102 is connected, thus tends to assume a potential relatively close to the potential of the negative bus conductor 41. The base is thus negative with respect to the emitter of transistor 102 which is connected to the positive bus conductor 44. As the motor 57 drives the timer to set the same, the wiper 61 of rheostat 62 rotates in a counterclockwise direction, as previously pointed out, increasing the effective resistance between negative bus conductor 41 and the junction point 117 and hence increasing in a positive direction the potential of junction 117. As la. certain point in the rotation of wiper 61, depending upon the voltage across the output terminals 11 and 12, the potential of junction point 117 becomes suiciently high with respect to the potential of the emitter of transistor 102, that current ows through the base emitter circuit to cause he transisor 102 to become conductive. When this happens, transistor 97 is rendered nonconductive; this, in turn, causing transmitter 84 to become nonconductive. Since the original energizing circuit to the relay winding 67 through the switch 75 has been interrupted due to the release of the pushbutton 78, the only circuit to maintain relay winding 67 energized is the circuit through transistor 84, previously traced. Thus, when transistor 84 becomes nonconductive, the relay coil 67 is de-energized, allowing the switch blades 68 and 69 to move back into engagement with contacts 70 and 71. The movement of switch blades 68 and 69 out of engagement with contacts 72 and 73 and into engagement with contacts 70 and 71 results in several actions taking place.

In the first place, the previously traced circuit through the timer setting motor 57 included contact 72. As soon as the switch blade 68 separates from contact 72, the motor 57 becomes de-energized so as to no longer drive the setting mechanism of the timer. In the second place, the primary winding 86 of transformer 85 is de-energized, the circuits energized by it being no longer necessary in the operation. The de-energization of primary winding 86 removes the voltage between conductors 93 and 44 so that there is no longer any voltage available for energization of relays 140 and 141 so that the relay combination which has been energized becomes de-energized, thus disconnecting the load resistance from across the battery 13.

The movement of relay switch blade 68 into engagement with contact 70 also establishes an energizing circuit to the primray winding 20 of the main transformer 19 for supplying charging current to the battery. This circuit may be traced as follows: from input terminal 15, through conductor 150, switch blade 68, contact 70, conductor 175, timer contact 50, timer switch blade 49, conductors 176 and 177, selector switch blade 31, the selected one of contacts 27, 28, 29 and 30, primary winding 20 and conductors 22, 23, 24, 25 and 26 back to the other input terminal 14. The main transformer 19 is now energized to supply charging current to the battery 13.

At the same time, an energizing circuit is established to the timer motor 45 through switch blade 68, contact 70, conductor 175, the timer contacts 49 and 50, conductor 176, timer motor 45, and conductors 178, 25 and 26 back to the other input terminal. The tim-er motor is now effective to drive the timer cam 48 in the same direction, this movement being possible because of the one-way` clutch 56 which makes possible continued movement of the timer in the same direction as it was advanced by the setting motor 57, despite the fact that the setting motor 57 is now de-energized.

In tracing the previously mentioned circuits to the primary 20 of transformer 19 and to the timer motor 45, the circuits traced inclu-ded the timer motor switch blade 49 and contact 50. It is, of course, understood, as previously explained, that when the setting motor 57 operates to set the timer, the cam 48 is rotated away from the position shown to allow movement of switch blade 49 into engagement with contact 50. Thus, at any time that the timer setting motor 57 has set the timer sufficiently to cause transistor 84 to become nonconductive and drop out-relay y67 in the manner previously described, the switch blade 49 will be engaged with Contact 50 to permit closure of the two circuits just traced.

The fan 150 is maintained energized both during the time during which the timer is being set and also during the charging operation. The circuit to the fan motor during the timer setting operation was previously traced. When relay 66 drops out causing movement of switch blade 69 into engagement with contact 71, a circuit is established to the fan motor 149, from input terminal 15, through conductor 150, relay switch blade 68, contact 70,y conductor 175, timer contacts 50 and 49, conductors 176, 177 and 179, relay contact 71, switch blade 69, conductor 164, fan ymotor 149 and conductors 23, 24, 25 and 26 back to the other input terminal 14.

The effect of switch 125 in shorting out the rheostat 111 and resistor 110 when a l2-volt battery is connected has previously been referred to. With the above explanation of the operation in mind, it will be apparent that the shorting out of rheostat 111 and resistor 110` tends to shift the potential of junction point 117, to which the base transistor 102 is connected, in the direction of the positive potential of junction 108. This tends to compensate for the fact that with the 12Volt battery connected between conductors 41 and 44, the potential of conductor 41 to which resistor 116 is connected is much more negative with respect to conductor 44 than is the case when a 6-volt battery is connected. Thus, in order to compensate for the more negative potential to which the one end of the voltage divider is connected, it is desirable to remove some of the resistance in the leg of the voltage divider in the other side of junction point 117, When, on the other hand, a 6-volt battery is connected across the output terminals 11 and 12 and hence across conductors 41 and 44, both rheostats 111 and 112 and resistors 110 and 113 are maintained in this leg of the voltage divider since the negative voltage between conductor 41 and conductor 44 is less than with a l2-volt battery.

It is, of course, understood that the rheostats 115, 111 and 112 are provided for Calibrating purposes to insure that the setting of the timer at which the charging operation begins bears a proper relation to the battery voltage. Normally, these are initially set during the calibration of the apparatus and need not be adjusted thereafter.

Due to the fact that the voltage across the battery is compared with the fixed voltage across the Zener diode 106, which voltage remains extremely constant throughout the life of the apparatus, there is very little danger that any recalibration of the apparatus is ever necessary.

The apparatus thus has the distinct advantage over one employing, for example, a meter movement in which the calibration can change with age.

Reference has been made to one or both of the two load resistors 147 and 148 being connected across the battery during the time in which the timer was being set and being disconnected when the charging operation was started. The reason for this is that it has been found that a much more realistic measure of the battery voltage for determining the direct charging period is obtained if the Voltage is measured while the battery is under load, as distinguished from an open circuit voltage of the battery. During the charging operation, it would, of course, be undesirable to have either of the load resistances connected across the battery since the charging current would tend to flow through the load resistance.

The operator is aware when the charging cycle has been inititted by the extinguishment of a light 190. This light 190 is connected across the power supply provided by transformer 85, being connected in parallel with the filter condenser 94. When transformer is rst energized this light which will take the form of any suitable electric lamp, located on a panel so as to be visible to the operator, becomes illuminated. As soon as the setting of the timer has been completed to result in the de-energization of relay 66, transformer primary 86is de-energized as previously described. This also results in the de-energization of the light 190. The operator now knows that the charging cycle has been initiated.

As soon as the charging cycle is initiated, the operator looks at meter 184 which, as previously explained, is connected across the output terminals 11 and 12. If a l2 volt battery is being charged, the rheostat 181 is connected in parallel with meter 184 and resistor 185 through switch contact and switch blade 127 as previously described. If, on the other hand, a 6-volt battery is being charged so that the selector switch 125 is in the 6-volt position, the connection of rheostat 185 in parallel with meter 184 is interrupted. In this way, the meter 184 is unaffected by the rated voltage of the battery being charged.

The operator now adjusts the switch blade 31 until the pointer of the meter 184 assumes a predetermined position, indicating that the desired charging rate has been selected. By the use of meter 184, the charging rate selected is dependent not only upon the capa-city of the batteiy but also, to some extent, upon its condition.

The charging operation now proceeds at the desired charging rate. The timer motor 45 continues to drive the timer in the direction shown in the drawing, towards its zero position.

After a predetermined period of time, depending upon the extent to which the timer was advanced during the l 1 setting operation, the timer will move to its zero position at which time the switch blade 49 will separate from contact 50 to interrupt the circuits to the primary 20 of transformer 19 to the timer motor 46 and to the fan 149.

It will be seen from the foregoing description that all that is necessary to do to start the charging operation is to momentarily push the button 78 of the momentary contact switch 75. As soon as switch blades 76 and 77 are closed, the entire operation is initiated and the button 78 can then be released with the assurance that the timer will be set to the correct timing position, and that the charging operation will be initiated. After that, all the operator has to do is to observe meter 184 and set the desired charging rate. The charging operation then continues and automatically terminates when the battery has been charged for the time selected by the timer setting motor. The apparatus thus requires a minimum amount of skill on the part of the operator.

While I have shown a specific embodiment of my invention, it is to be understood that the scope of the invention is to be limited solely by the appended claims.

I claim:

1. In a battery charging apparatus, means for producing a charging current including input terminals adapted to be connected to a source of electrical energy,

output terminals to which said charging current is applied and adapted to be connected to a battery to be charged;

a switching device controlling the connections between said input terminals and said output terminals to control the application of said charging current to said output terminals;

a timer which can be adjusted from an off position to any of various selected initial timing positions and then moves at a timed rate to said off position,

said timer having a switch operated thereby and effectively connected between said input and output terminals to prevent said charging current from being applied to said output terminals when said timer moves to said oft position, and

said timer having a variabe impedance adjusted thereby and eiective when said timer is adjusted to be correspondingly varied;

control circuit means connected to said variable impedance, said switching device and said output terminals effective when said output terminals are connected to a battery to be charged and when said timer and said variable impedance are adjusted to a position depending upon the voltage output of the battery to be charged to affect the operation of said switching device in such a manner that said source can be effectively connected to said output terminals;

a motor for adjusting said timer;

means for energizing said motor;

and means controlled by said switching device for terminating energization of said motor as a result of said timer and variable impedance being adjusted to a position dependent upon the voltage output of the battery to be charged.

2. The apparatus of claim 1 in which there is a voltage reference device connected to a source of voltage and having a constant voltage drop thereacross and in which the 12 control circuit means controls the switching device in accordance with the relative value of this constant voltage drop and the voltage output of the battery to be charged.

3. The apparatus of claim 1 in which the switching device is a relay which is initially actuated to initiate the operation of the motor for adjusting the timer and is then released when said timer is set by the desired amount to terminate operation of said motor and initiate the charging operaiton.

4. The apparatus of claim 1 in which there is a load resistance and means for connecting said load resistance across the output terminals during the period of time in which said motor is adjusting said timer.

5. The apparatus of claim 4 in which there is an electrically controlled cooling device and in which said cooling device is energized through one circuit while said load resistance is connected across the battery and through another circuit during the charging operationA 6. The apparatus of claim 4 in which there is a selectively operable means connected to said load resistance for selecting the amount of load resistance connected across the output terminals depending upon the normal votage output of the battery being charged.

7. The apparatus of claim 6 in which means controlled by said selectively operable means affects the response of said control circuit means to the battery output voltage in accordance with the normal output voltage of such battery.

8. The apparatus of claim 1 in which the switching device is a relay controlled by a solid state electronic device and in which said control circuit means controls the votage applied to the input terminals of said electric device.

9. The apparatus of claim 8 in which the relay has an operating winding and a switch controlled thereby and moved to circuit closed position upon energization of said winding and in which said operating winding is in series with the output terminals of said electronic device and said switch is connected in series with said input terminals.

10. The apparatus of claim 1 in which the motor is connected to said timer by a one-way clutch which is efcctive to cause said motor to adjust said timer but is ineffective to retard the movement of said timer to said oit' position independently of said motor.

References Cited UNITED STATES PATENTS 2,431,707 12/1947 Pugh 320-38 X 2,432,069 12/l947 Pugh S20-38 X 3,178,629 4/1965 Saslow 320-30 X 3,200,303 8/1965 Maxwell 307-141 X 3,246,182 4/ 1966 Hanchett 307-141 3,388,566 6/1968 Kaper et al. 307-141 X JOHN F. COUCH, Primary Examiner STANLEY WEINBERG, Assistant Examiner U.S. Cl. X.R. 

